Add support for using text_style in format and vformat directly (#993)

include/fmt/color.h

@@ -452,6 +452,13 @@ struct ansi_color_escape {
   }
   FMT_CONSTEXPR operator const Char *() const FMT_NOEXCEPT { return buffer; }
 
+  FMT_CONSTEXPR const Char * begin() const FMT_NOEXCEPT {
+    return buffer;
+  }
+  FMT_CONSTEXPR const Char * end() const FMT_NOEXCEPT {
+    return buffer + std::strlen(buffer);
+  }
+
 private:
   Char buffer[7u + 3u * 4u + 1u];
 
@@ -502,6 +509,13 @@ inline void reset_color<wchar_t>(FILE *stream) FMT_NOEXCEPT {
   fputs(internal::data::WRESET_COLOR, stream);
 }
 
+template <typename Char>
+inline void reset_color(basic_memory_buffer<Char>& buffer) FMT_NOEXCEPT {
+  const char* begin = data::RESET_COLOR;
+  const char* end = begin + sizeof(data::RESET_COLOR) - 1;
+  buffer.append(begin, end);
+}
+
 // The following specialiazation disables using std::FILE as a character type,
 // which is needed because or else
 //   fmt::print(stderr, fmt::emphasis::bold, "");
@@ -510,6 +524,37 @@ template <>
 struct is_string<std::FILE *> : std::false_type {};
 template <>
 struct is_string<const std::FILE *> : std::false_type {};
+
+template <typename Char>
+std::basic_string<Char> vformat(
+    const text_style &ts, basic_string_view<Char> format_str,
+    basic_format_args<typename buffer_context<Char>::type> args) {
+  basic_memory_buffer<Char> buffer;
+  bool has_style = false;
+  if (ts.has_emphasis()) {
+    has_style = true;
+    ansi_color_escape<Char> escape =
+      make_emphasis<Char>(ts.get_emphasis());
+    buffer.append(escape.begin(), escape.end());
+  }
+  if (ts.has_foreground()) {
+    has_style = true;
+    ansi_color_escape<Char> escape =
+      make_foreground_color<Char>(ts.get_foreground());
+    buffer.append(escape.begin(), escape.end());
+  }
+  if (ts.has_background()) {
+    has_style = true;
+    ansi_color_escape<Char> escape =
+        make_background_color<Char>(ts.get_background());
+    buffer.append(escape.begin(), escape.end());
+  }
+  internal::vformat_to(buffer, format_str, args);
+  if (has_style) {
+    reset_color<Char>(buffer);
+  }
+  return fmt::to_string(buffer);
+}
 } // namespace internal
 
 template <
@@ -570,6 +615,35 @@ typename std::enable_if<internal::is_string<String>::value>::type print(
   return print(stdout, ts, format_str, args...);
 }
 
+
+template <typename S, typename Char = FMT_CHAR(S)>
+inline std::basic_string<Char> vformat(
+    const text_style &ts,
+    const S &format_str,
+    basic_format_args<typename buffer_context<Char>::type> args) {
+  return internal::vformat(ts, to_string_view(format_str), args);
+}
+
+/**
+  \rst
+  Formats arguments and returns the result as a string using ANSI
+  escape sequences to specify text formatting.
+
+  **Example**::
+
+    #include <fmt/color.h>
+    std::string message = fmt::format(fmt::emphasis::bold | fg(fmt::color::red),
+                                      "The answer is {}", 42);
+  \endrst
+*/
+template <typename S, typename... Args>
+inline std::basic_string<FMT_CHAR(S)> format(
+    const text_style &ts, const S &format_str, const Args &... args) {
+  return internal::vformat(
+    ts, to_string_view(format_str),
+    *internal::checked_args<S, Args...>(format_str, args...));
+}
+
 #endif
 
 FMT_END_NAMESPACE

test/format-impl-test.cc

@@ -206,7 +206,7 @@ TEST(FormatTest, CountCodePoints) {
   EXPECT_EQ(4, fmt::internal::count_code_points(fmt::u8string_view("ёжик")));
 }
 
-TEST(ColorsTest, Colors) {
+TEST(ColorsTest, ColorsPrint) {
   EXPECT_WRITE(stdout, fmt::print(fg(fmt::rgb(255, 20, 30)), "rgb(255,20,30)"),
                "\x1b[38;2;255;020;030mrgb(255,20,30)\x1b[0m");
   EXPECT_WRITE(stdout, fmt::print(fg(fmt::color::blue), "blue"),
@@ -244,3 +244,35 @@ TEST(ColorsTest, Colors) {
                fmt::print(bg(fmt::terminal_color::bright_magenta), "tbmagenta"),
                "\x1b[105mtbmagenta\x1b[0m");
 }
+
+TEST(ColorsTest, ColorsFormat) {
+  EXPECT_EQ(fmt::format(fg(fmt::rgb(255, 20, 30)), "rgb(255,20,30)"),
+            "\x1b[38;2;255;020;030mrgb(255,20,30)\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::color::blue), "blue"),
+            "\x1b[38;2;000;000;255mblue\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::color::blue) | bg(fmt::color::red), "two color"),
+            "\x1b[38;2;000;000;255m\x1b[48;2;255;000;000mtwo color\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::emphasis::bold, "bold"),
+            "\x1b[1mbold\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::emphasis::italic, "italic"),
+            "\x1b[3mitalic\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::emphasis::underline, "underline"),
+            "\x1b[4munderline\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::emphasis::strikethrough, "strikethrough"),
+            "\x1b[9mstrikethrough\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::color::blue) | fmt::emphasis::bold, "blue/bold"),
+            "\x1b[1m\x1b[38;2;000;000;255mblue/bold\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::emphasis::bold, "bold error"),
+            "\x1b[1mbold error\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::color::blue), "blue log"),
+            "\x1b[38;2;000;000;255mblue log\x1b[0m");
+  EXPECT_EQ(fmt::format(fmt::text_style(), "hi"), "hi");
+  EXPECT_EQ(fmt::format(fg(fmt::terminal_color::red), "tred"),
+            "\x1b[31mtred\x1b[0m");
+  EXPECT_EQ(fmt::format(bg(fmt::terminal_color::cyan), "tcyan"),
+            "\x1b[46mtcyan\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::terminal_color::bright_green), "tbgreen"),
+            "\x1b[92mtbgreen\x1b[0m");
+  EXPECT_EQ(fmt::format(bg(fmt::terminal_color::bright_magenta), "tbmagenta"),
+            "\x1b[105mtbmagenta\x1b[0m");
+}